Such a spray ring and wetting method may be used in a gasification reactor of a coal gasification plant, or in any other reactor wherein char and/or slag is quenched in a water slag bath. For the purpose of this specification, char refers to solid ash and slag refers to liquid ash.
In a coal gasification plant a pulverised carbonaceous fuel, such as coal, is transformed into a product gas consisting mainly of synthesis gas. The gasification plant typically comprises a gasification reactor, or gasifier, wherein the pulverised carbonaceous fuel is gasified under high pressure and high temperature conditions. In such a gasifier, a wall surface is provided on which a slag can form out of the ashes. Such a wall surface can be provided in the form of a membrane wall.
The slag is allowed to drip down along the wall surface, where it is collected in a slag water bath where it can cool and solidify. In the art, a spray ring is used to spray the slag particles on or near the water surface of the slag water bath, for facilitating the sinking of the slag for removal from below the slag water bath.
A spray ring for use as a wetting device for wetting char and slag in a slag water bath below a coal gasification reactor is described in European patent application EP-A 0 318 071. This spray ring is based on a circular conduit extending in a horizontal plane. The spray ring contains recycled water from the slag bath, and possibly a wetting agent, and is provided with threaded ports for holding changeable nozzles. The circular conduit is connected to a supply duct for supplying the water, which extends perpendicularly from the circular conduit out of the plane in which the circular conduit extends. The nozzles must have a diameter that lies within a pre-determined range in order to yield a sufficient velocity of the sprayed water while preventing the nozzles from plugging with solids contained in the water recycled to the circular conduit.
The spray ring described in EP-A 0 318 071 suffers from settlement of solid particles from the recycled water.